The top economic planning agency in Kunming city has called in the police after a sex tape allegedly featuring one of its officials was widely circulated online.

Video screen grabs, dated January 1, 2007 and featuring four naked men and women on a bed, were posted on an online discussion board on Sunday. The person who posted them said he obtained the video on a portable hard drive he came across.

One of the participants in the photos is said to be Cheng Jianjun from the Kunming Municipal Commission of Development and Reform. The person posting the video claimed it was Cheng, using other information found on the hard drive.

'A portable drive was found in a room of a Kunming sauna parlour. I opened it after reaching home and found a self-captured video featuring group sex,' the person said.

'If anyone knows this man, please call me so that I can return his lost drive. If Kunming's disciplinary committee has seen this post, please contact me as well.'

A commission spokesman said the man highlighted in the photos was the deputy head of the commission's fee-collection department, but he said the deputy's image had been edited into the pictures with malicious intent.

He said the Kunming government had set up an investigation team to handle the incident after reporting the case to local police. He could not comment further until the investigation was completed.

As of yesterday, Cheng was still working at the commission, but had been assigned to other duties.

The Southern Metropolis News reported yesterday that Cheng demanded that the posts be removed from internet discussion boards, but the photos are still being widely circulated online. Cheng reportedly denied having lost a portable hard drive and said he was blackmailed before the photos appeared online.

Meanwhile, in Henan province, disciplinary committee investigators of Luoyang city are investigating a sex-photo scandal in which a senior official of Ruyang county was allegedly implicated.

Ma Zhanbiao, head of the Ruyang's People Congress, has been accused of taking sexual advantage of a retired factory worker and of photographing himself having sex with her.

The alleged photos were posted on discussion forums yesterday but mainland media, citing an official response, said the content of the internet post was not accurate.